Multi-purpose utility of constructing 3D static Geomechanical model in the Ichthys field, Browse Basin

The petroleum industry progressed significantly to develop 3D/4D geomechanical models (GMs) to make efficient field development planning which reduces the uncertainty of 1D GM in the field scale. In this paper, we demonstrated how to build a high-resolution 3D static GM in a stratigraphic structural setup with a combination of wireline logs, drilling data, structural objects, and laboratory rock mechanical data from 21 core samples in the Ichthys field of the Browse Basin, North West Shelf so that spatial distribution of pore pressure and stress behaviour can be understood across the Brewster Member sandstone reservoir. The workflow incorporates calibrated 1D GM of seven wells. 1D GM analysis confirmed strike-slip faulting regime throughout the stratigraphic column and the orientation of maximum principal stress is nearly towards the E-W direction. The 1D model also indicates a sharp pressure ramp within Jamieson reaching a maximum to the middle of the layer and then regressed below Aptian and near to hydrostatic pressure at top of the upper Vulcan formation. 3D modelling is performed by incorporating interpreted seismic surfaces and unconformities in line with the geological understanding of the subsurface and stratigraphic variation from the seabed to lower Vulcan formation. A geostatistical technique is adopted to map and interpolate rock properties throughout the grid which is tied with the field's stratigraphic unit. A seismic velocity cube is used to compute density profile based on acoustic-density correlation and thereafter vertical stress. Pore pressure is modelled by defining the pressure depth relationship from the 1D reference pore pressure profile and honouring the structural layering. Due to its inherent property of structural consistency, this 3D model efficiently captures the lateral heterogeneity over the 1D model validated at Prelude-1A well location.